1. Field of the Invention
This invention relates to a process for manufacturing sacks, bags, or the like, hereinafter referred to as "sacks", and more particularly to a process including a tube-making step and bottom-closing step, especially advantageously adaptable for manufacturing heavy duty sacks.
2. Description of the Prior Art
There is a conventionally known process for manufacturing heavy-duty sacks, comprising mainly of a step for making tube segments from sheet material, such as, kraft paper, and a bottom-closing step that includes sewing, stitching, or pasting the bottoms of the tube segments. The tube segments are discharged in a flat form from the tube-making station, are usually stacked manually on a pallet, and the stacked tube segments are pressed, for instance, by placing a suitable weight on top of the stack them until the longitudinal paste, having been applied to the tube during the tube-making step, has dried. After being dried, the tube segments are removed from the pallet and are manually charged one by one into the bottom-closing station.
Recently, in order to increase the production-rate and eliminate some of the manual labor involved, an automatic tube feeder is used to supply the tube segments to the bottom-closing station. However, it is still necessary to manually charge the automatic tube feeder with packets of 20 to 30 tube segments.
According to these conventional processes during the period in which the tube segments are in stacks, after discharge from the tube-making station, the tube segments are subjected to "waving" or "undulation", which can have an adverse affect on the bottom-closing process, causing the production of unacceptable quality sacks.
To solve the above-mentioned problems, a method has been proposed for directly connecting the tube-making station with the bottom-closing station by a conveyor-system. However, this conveyor must be extremely long, since the tube segments must be kept under pressure until the longitudinal paste has dried, as mentioned above, which means that a large area must be provided for the conveyor-system, making the proposed method both expensive and uneconomical.
In another prior art, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 52-44973, in order to store or transport sacks discharged at a high speed from a sack-making machine, or to thereafter prepare the finished sacks for separating them from each other and supplying them to a sack-filling station, the sacks are overlapped or shingled in the longitudinal or axial direction of the finished sacks, and are wound into a reel with the help of winding tapes.
Hithertobefore, however, it has been unknown that, in a sack manufacturing process, the open-ends tube segments discharged from the tube making step are overlapped or shingled as offset by a certain distance and fed to be wound on a reel in the direction perpendicular to the discharging or longitudinal direction of the tube segments with the help of winding tapes, and thereafter the tube segments are unwound being synchronized with the bottom-closing step and separated from each other to supply them into a bottom-closing step where one or both ends (bottoms) of the tube segments are closed.